BFS打印路径——1076. 迷宫问题

 可以用两种方式输出路径，一个正向（需要借助栈），一个是反向；

BFS正向打印路径：

#include <iostream>
#include <cstring>
#include <queue>
#include <stack>
#define x first
#define y second
using namespace std;
const int N = 1010;
typedef pair<int,int>PII;
int g[N][N];
PII pre[N][N];
queue<PII> q;
int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
int n;

void bfs(int sx, int sy)
{
    memset(pre, -1, sizeof pre);
    pre[sx][sy] = {N, N};
    q.push({sx, sy});
    while(q.size())
    {
        auto t = q.front(); q.pop();
        int xx = t.x, yy = t.y;
        for(int i = 0; i < 4; i++)
        {
            int x = dx[i] + xx, y = dy[i] + yy;
            if(!g[x][y] && x >= 0 && x < n && y >= 0 && y < n && pre[x][y].y == -1)
            {
                pre[x][y] = t;
                q.push({x,y});
            }
        }
    }
}
int main()
{
    scanf("%d", &n);
    for(int i = 0; i < n; i++)
        for(int j = 0; j < n; j++)
            scanf("%d", &g[i][j]);
    bfs(0,0);

    int x = n - 1, y = n - 1;
    stack<PII>s;
    while(x || y)
    {
        s.push({x,y});
        auto t = pre[x][y];
        x = t.x, y = t.y;
    }
    s.push({0,0});
    while(s.size())
    {
        auto t = s.top(); s.pop();
        printf("%d %d\n", t.x, t.y);
    }

    return 0;
}

BFS逆向打印路径：(我吐了，输入图的时候忘记加&了，找了半天)

#include <iostream>
#include <queue>
#include <cstring>
#define x first
#define y second
using namespace std;
typedef pair<int,int>PII;
const int N = 1010;
int g[N][N];
PII pre[N][N];
queue<PII>q;
int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
int n;

void bfs(int sx, int sy)
{
    memset(pre, -1, sizeof pre);
    pre[sx][sy] = {n,n};
    q.push({sx, sy});
    while(q.size())
    {
        auto t = q.front(); q.pop();
        int xx = t.x, yy = t.y;
        for(int i = 0; i < 4; i++)
        {
            int x = xx + dx[i], y = yy + dy[i];
            if(!g[x][y] && x >= 0 && x < n && y >= 0 && y < n && pre[x][y].y == -1)
            {
                pre[x][y] = t;
                q.push({x,y});
            }
        }
    }
}
int main()
{
    scanf("%d", &n);
    for(int i = 0; i < n; i++)
        for(int j = 0; j < n; j++)
            scanf("%d", &g[i][j]);

    bfs(n-1, n-1);

    int x = 0, y = 0;
    while(x != n || y != n)
    {
        printf("%d %d\n", x, y);
        auto t = pre[x][y];
        x = t.x, y = t.y;
    }

    return 0;
}

标签：pre,sy,sx,1076,迷宫,BFS,int,&&,include
来源： https://www.cnblogs.com/MoonSkyy/p/15938661.html